Meso-substituted liquid porphyrins

Article abstract of DOI:10.1002/asia.200900693

Meso-substituted A₄-porphyrins bearing 3,4,5-trialkoxyphenyl substituents are efficiently synthesized and characterized. Porphyrins bearing twelve C10 and C11 alkyl chains turned out to be liquid at room temperature. The remaining porphyrins, b

Full text of DOI:10.1002/asia.200900693

FULL PAPERS
DOI: 10.1002/asia.200900693
Meso-Substituted Liquid Porphyrins
Agnieszka Nowak-Krꢀl, Dorota Gryko, and Daniel T. Gryko*[a]
Abstract: Meso-substituted A4-porphyrins bearing 3,4,5-trialkoxyphenyl substitu-
ents are efficiently synthesized and characterized. Porphyrins bearing twelve C10
Keywords: aldehydes · calorimetry ·
liquids · optical limiters · porphyri-
noids
and C11 alkyl chains turned out to be liquid at room temperature. The remaining
porphyrins, bearing C8, C9, C12, and C18 alkyl chains, have low melting points
and high solubility in nonpolar solvents. Their differential scanning calorimetry
distinctly shows, in most cases, only one phase transition.
Introduction
Our aim was not only to synthesize liquid porphyrins but
also to identify patterns of substituents which can subse-
quently be used in the synthesis of more complex two-
photon absorbing porphyrins.[8] For this reason, we focused
on electron-donating groups which, suitably placed, are
known to increase 2PA.[7b,9] Screening of a variety of differ-
ent substituent arrangements allowed the identification of
the 3,4,5-trialkoxyphenyl moiety as a promising lead. The in-
fluence of n-alkyl chains on melting points of various aro-
matic compounds has been broadly explored,[4c,j,l–o,10] includ-
ing the 3,4,5-trialkoxyphenyl moiety, which was utilized in
the design of liquid crystals.[10b–f,11] The 3,4,5-trialkoxyphenyl
structural motive was also often used in conjunction with
the studying of dye aggregation,[12,13] self-assembling den-
drimers,[14] chiral liquid crystals,[15] and ionic liquid crys-
An intrinsic property of planar aromatic systems is their ten-
dency to form stacks and aggregates which eventually results
in low solubility, high crystallinity, and high melting point.[1]
This also holds true for porphyrins and phthalocyanines.[2]
The design and synthesis of porphyrins which are liquids at
room temperature is a formidable scientific challenge and to
the best of our knowledge, no single solution has been re-
ported. The first porphyrins which displayed liquid crystal-
line properties were reported by Goodby et al. in 1980.[3] In
the following years many porphyrinoids which are liquid
crystals[4] as well as liquid phthalocyanines[5] were described
in the literature. Complex, dendritic porphyrins with low
melting points have also been known for some time.[6] At
the same time, liquidity is also a prerequisite to their appli-
cation as real-world optical limiters.[7] As part of a broader
project, we decided to tackle the problem of the design and
synthesis of porphyrin-based optical limiters possessing a
high two-photon absorption (2PA) cross-section combined
with reverse-saturable absorption. Among many different
architectures, we focused on meso-substituted A4-porphyrins
bearing substituted phenyl groups. Herein, we report the
synthesis and characterization of a homologous series of
porphyrins with very low melting points.
AHCTUNGTRENNUNG
tals.[11a]
Results and Discussion
Easily available 3,4,5-trihydroxybenzaldehyde[16] (1) was al-
kylated under classical Williamson conditions with alkyl bro-
mides or iodides to give a set of 3,4,5-trialkoxybenzalde-
hydes 3a–f (Scheme 1). The alkyl chain length ranged from
8 to 18 carbon atoms. The resulting aldehydes 3a–f were re-
acted with pyrrole under Lindseyꢀs co-catalysis conditions[17]
to give A4-porphyrins 4a–f in 36–53% yield (Scheme 1).
These high yields together with straightforward purification
allowed the preparation of porphyrins 4a–f at a scale of
around 200 mg. All porphyrins were highly soluble in organ-
ic solvents such as hexanes, diethyl ether, ethyl acetate, and
so forth. Residual solvents were removed by drying for 72 h
under high vacuum, and allowed the identification of por-
phyrins which are liquid at room temperature.
[a] A. Nowak-Krꢁl, Dr. D. Gryko, Prof. D. T. Gryko
Institute of Organic Chemistry
Polish Academy of Sciences
Kasprzaka 44/52, 01-224 Warsaw (Poland)
Fax : (+48)22-6326681
E-mail: daniel@icho.edu.pl
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.200900693.
904
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2010, 5, 904 – 909

Figure 1. DSC curves for 4d: a) reheating; and b) the second cooling
(heating rate/cooling rate: 58C minꢀ1).
Table 1. Calorimetric data for compounds 4a–f[a]
Compound n[b] Transition
T [8C]
Onset Maximum
.
DH [kJmolꢀ1
]
4a
4b
4c
4d
4e
8
9
10
11
12
Cry[c]!Iso[d]
55.1
26.2
56.8
27.3
78.1
25.1
11.5
33.6
47.1
7.32
284.9
Cry!Iso
Cry!Iso
ꢀ54.6 ꢀ39.7
Scheme 1. Synthesis of porphyrins 4a–f.
Cry!Iso
ꢀ23.8 ꢀ17.8
Cry(I)!Cry(II)
Cry(II)!Iso
Cry!Iso
32.0
36.4
44.0
34.6
38.4
46.6
4f
18
Subsequently, the thermal behavior of the porphyrins was
investigated by differential scanning calorimetry (DSC). An
exemplary DSC of porphyrin 4d is presented in Figure 1.
The results obtained from DSC analysis of porphyrins 4a–f
are summarized in Table 1 and Figure 2. All the tempera-
tures represent the peak onset temperature of the DSC
curves.
[a] Temperature and enthalpy changes were obtained by reheating the
samples. [b] The length of the alkyl chain. [c] Crystal. [d] Isotropic liquid.
The data presented for 4a shows that during heating/cool-
ing cycles from 108C to 708C, a large sharp endothermic
peak was observed at ca. 558C with almost equal enthalpy
changes (DH), which can clearly be attributed to fusion of
4a. However, on cooling from 708C no peak was observed,
signifying that material stayed in the liquid state until 108C.
A similar supercooling effect was also observed in the case
of porphyrins 4b, 4c, and 4e. Additionally, porphyrin 4e ex-
hibits the crystal Cry(I)–crystal Cry(II) phase transition, the
´´
Abstract in Polish: Zsyntetyzowano szesc mezo podstawio-
Figure 2. The melting points of porphyrins 4a–4 f (&) and enthalpy of
phase transition (*) as a function of alkyl chain length; the phase transi-
tion temperatures represent the peak onset in the DSC (n is number of
carbon atoms in aliphatic chain).
nych porfiryn zawieraja˛cych podstawniki 3,4,5-trialkoksyfe-
nylowe. Porfiryny z łancuchami alkilowymi zawieraja˛cymi
dziesie˛c i jedenascie atomꢁw we˛gla sa˛ cieczami w tempera-
´
´
´
turze pokojowej. Pozostałe cztery porfiryny wykazuja˛
´´
bardzo dobra˛ rozpuszczalnosc w rozpuszczalnikach niepolar-
crystal Cry(II) melts to isotropic liquid at ca. 368C. The
large enthalpy change for isotropization of 4e porphyrin
and the strong supercooling effect indicate that Cry(II) is a
solid crystal rather than liquid crystal. This is also confirmed
nych oraz niskie temperatury topnienia. Badania metoda˛
´
skaningowej kalorymetrii rꢁz˙nicowej wykazały dla wie˛kszos-
´
ci porfiryn tylko jedno przejscie fazowe.
Chem. Asian J. 2010, 5, 904 – 909
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www.chemasianj.org
905

D. T. Gryko et al.
FULL PAPERS
by polarized optical microscopy (POM). The striking differ-
ence between the physical state at room temperature is ex-
emplified by comparison of porphyrins 4a and 4c in polar-
ized light (Figure 3).
Experimental Section
General
All chemicals were used as received unless otherwise noted. Reagent
grade solvents (CH2Cl2, hexanes) were distilled prior to use. All reported
1H NMR and 13C NMR spectra were collected using a 500 or 600 MHz
spectrometer. Chemical shifts (d ppm) were determined with TMS as the
internal reference; J values are given in Hz. The UV/Vis absorption spec-
tra were recorded in CH2Cl2. The absorption wavelengths are reported in
nm with the extinction coefficient in Mꢀ1 cmꢀ1 in brackets. Melting points
of aldehydes were determined using a capillary type apparatus. Melting
points of porphyrins were determined by means of DSC apparatus. Purge
gas is high purity nitrogen. All the temperatures collected represent the
peak onset temperature of the DSC curves. The heating rate is given in
brackets. The enthalpies (DH) are the thermodynamics parameters of
these temperature variation processes which were estimated from each
DSC peak area computed by standard procedure in DSC apparatus.
Chromatography was performed on silica (200–400 mesh) or alumina.
Dry column vacuum chromatography (DCVC) was performed on prepa-
rative thin-layer chromatography silica. The mass spectra were obtained
by field desorption MS (FD-MS) or electron impact MS (EI-MS).
Figure 3. POM of porphyrins 4a (a) and 4c (b) at RT.
Porphyrin 4c melts at ꢀ558C and it shows only a crystal–
isotropic liquid phase transition. An analogous situation
occurs also for porphyrins 4a, 4b, 4d, and 4 f. In the case of
4d and 4 f the degree of supercooling is low, mainly ca. 38C
for 4d and 2.58C for 4 f. Upon heating both compounds un-
dergo single phase transitions (Cry!Iso) at ꢀ248C and
448C, respectively. Upon cooling 4d from the melt, a broad
exothermic peak was observed at ꢀ278C, and in the case of
4 f one strong exothermic peak at 41.58C is observed fol-
lowed by two very weak exotherms at 378C and 348C. The
behavior of the compounds in DSC thermograms is very
sensitive to the alkoxy chain lengths present in the molecule.
Increasing the length of the alkoxy side chains leads to a de-
crease in the temperature for the Cry!Iso phase transition
(porphyrins 4a to 4c), exhibiting a minimum for the decy-
loxy substituted compound 4c (ꢀ558C).
Synthesis
3,4,5-Trioctyloxybenzaldehyde (3a). To a solution of 3,4,5-trihydroxyben-
zaldehyde monohydrate (1; 1.12 g, 6.5 mmol) in DMF (40 mL), 1-iodooc-
tane (4.8 mL, 26.6 mmol) was added, followed by K2CO3 (2.42 g,
17,5 mmol). The reaction mixture was stirred for 24 h at 1608C. Subse-
quently, the mixture was poured into water (100 mL) and extracted with
EtOAc (3ꢃ30 mL). The organic layers were combined, dried (Na2SO4),
filtered, and evaporated affording brown oil. The crude product was
chromatographed (silica gel, hexanes/CH2Cl2 3:1 to 13:6) to obtain pure
aldehyde 3a (2.31 g, 72%) as a yellow oil. 1H NMR (600 MHz, CDCl3,
258C, TMS): d=0.87–0.90 (m, 9H, CH3), 1.26–1.37 (m, 24H, CH2), 1.46–
1.51 (m, 6H, CH2), 1.73–1.78 (m, 2H, CH2), 1.80–1.85 (m, 4H, CH2),
4.02–4.07 (m, 6H, OCH2), 7.08 (s, 2H, ArH), 9.83 ppm (s, 1H, CHO).
Other spectral and physical properties concur with published data.[10e]
Further elongation of the alkyl chain causes an increase in
the melting point (porphyrins 4d to 4 f). The dramatic
alkoxy-chain length dependent decrease in melting point for
compounds 4a to 4c may arise from the disruption of p–p
interactions and induction of weak hydrophobic interactions
between the porphyrins. The presence of twelve alkyl chains
serves as an effective steric stabilizer preventing porphyrin
aggregation.
3,4,5-Trinonyloxybenzaldehyde (3b). To a solution of 3,4,5-trihydroxy-
benzaldehyde monohydrate (1; 1.12 g, 6.5 mmol) in DMF (40 mL), 1-bro-
mononane (5.0 mL, 26.2 mmol) was added, followed by K2CO3 (2.42 g,
17,5 mmol) and KI (210 mg, 1.27 mmol). The reaction mixture was stirred
for 24 h at 1608C. Subsequently, the mixture was poured into water
(100 mL) and extracted with EtOAc (4ꢃ30 mL). The organic layers were
combined, dried (Na2SO4), filtered, and evaporated affording brown oil.
The crude product was chromatographed (silica gel, hexanes/CH2Cl2 3:1)
to obtain pure aldehyde 3b (3.01 g, 87%) as a white solid. M.p.: 35.4–
36.48C; 1H NMR (500 MHz, CDCl3, 258C, TMS): d=0.87–0.90 (m, 9H,
CH3), 1.28–1.37 (m, 30H, CH2), 1.45–1.51 (m, 6H, CH2), 1.72–1.78 (m,
2H, CH2), 1.80–1.85 (m, 4H, CH2), 4.02–4.07 (m, 6H, OCH2), 7.08 (s,
2H, ArH), 9.83 ppm (s, 1H, CHO); 13C NMR (125 MHz, CDCl3, 258C,
TMS): d=14.1, 22.7, 22.7, 26.0, 26.1, 29.2, 29.3, 29.3, 29.4, 29.5, 29.6, 29.6,
30.3, 31.9, 31.9, 69.2, 73.6, 107.9, 131.4, 143.9, 153.5, 191.3 ppm. Other
spectral and physical properties concur with published data.[19]
Conclusions
In conclusion, we have identified structural features which
allow the synthesis of porphyrin architectures which are liq-
uids at room temperature.[18] 5,10,15,20-Tetrakis[3,4,5-tri(un-
decyloxy)phenyl]porphyrin and its decyloxy analogue are
both liquids at room temperature and have melting points
ꢀ248C and ꢀ558C, respectively. Considering that liquid por-
phyrins maintain the same spectroscopic features as their
solid analogues, this discovery not only opens the way to
design porphyrins possessing such substituents in optical
limiting devices but also allows its broader use in other ap-
plications where liquidity or very high solubility are desira-
ble.
3,4,5-Tridecyloxybenzaldehyde (3c). To a solution of 3,4,5-trihydroxyben-
zaldehyde monohydrate (1; 1.12 g, 6.5 mmol) in DMF (40 mL), 1-bromo-
decane (5.5 mL, 26.5 mmol) was added, followed by K2CO3 (2.42 g,
17,5 mmol) and KI (180 mg, 1.08 mmol). The reaction mixture was stirred
for 24 h at 1608C. Subsequently, the mixture was poured into water
(100 mL) and extracted with EtOAc (3ꢃ30 mL). The organic layers were
combined, dried (Na2SO4), filtered, and evaporated affording brown oil.
The crude product was chromatographed (silica gel, hexanes/CH2Cl2 3:1
to 13:7) to obtain pure aldehyde 3c (2.94 g, 79%) as a white solid. M.p.:
34.6–35.78C (lit. m.p.: 338C);[13] 1H NMR (600 MHz, CDCl3, 258C, TMS):
d=0.87–0.89 (m, 9H, CH3), 1.27–1.37 (m, 36H, CH2), 1.45–1.50 (m, 6H,
CH2), 1.73–1.77 (m, 2H, CH2), 1.80–1.85 (m, 4H, CH2), 4.02–4.07 (m,
6H, OCH2), 7.08 (s, 2H, ArH), 9.83 ppm (s, 1H, CHO). Other spectral
and physical properties concur with published data.[20]
3,4,5-Triundecyloxybenzaldehyde (3d). To a solution of 3,4,5-trihydroxy-
benzaldehyde monohydrate (1; 1.14 g, 6.6 mmol) in DMF (40 mL), 1-bro-
906
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ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2010, 5, 904 – 909

Meso-Substituted Liquid Porphyrins
moundecane (5.8 mL, 25.9 mmol) was added, followed by K2CO3 (2.42 g,
17,5 mmol) and KI (180 mg, 1.08 mmol). The reaction mixture was stirred
for 24 h at 1608C and further allowed to cool down to RT. The product
crystallized from the reaction mixture while cooling. The resulting solid
was washed with water, dissolved in EtOAc, and dried (Na2SO4). Then it
was filtered and evaporated to dryness to give a brown solid. Subsequent-
ly, the crude product was chromatographed (silica gel, hexanes/CH2Cl2
3:1 to 3:2) to obtain pure aldehyde 3d (3.57 g, 87%) which was recrystal-
lized (EtOH) to give colorless crystals. M.p.: 50.0–50.78C (EtOH);
1H NMR (500 MHz, CDCl3, 258C, TMS): d=0.88 (m, 9H, CH3), 1.27–
1.35 (m, 42H, CH2), 1.45–1.51 (m, 6H, CH2), 1.72–1.78 (m, 2H, CH2),
1.80–1.85 (m, 4H, CH2), 4.05 (m, 6H, OCH2), 7.08 (s, 2H, ArH),
9.83 ppm (s, 1H, CHO); 13C NMR (125 MHz, CDCl3, 258C, TMS): d=
14.1, 22.7, 26.0, 26.1, 29.3, 29.3, 29.4, 29.5, 29.6, 29.6, 29.7, 29.7, 31.9, 31.9,
69.3, 73.6, 107.9, 131.5, 143.9, 153.5, 191.2 ppm; HRMS (EI): m/z calcd
for C40H72O4: 616.5431; found: 616.5418; elemental analysis calcd (%) for
C40H72O4: C 77.87, H 11.76; found: C 77.61, H 11.90.
649 nm (5800); 1H NMR (500 MHz, CDCl3, 258C, TMS): d=ꢀ2.79 (brs,
2H, NH), 0.82–0.85 (m, 24H, CH3), 0.92–0.95 (m, 12H, CH3), 1.24–1.37
(m, 88H, CH2), 1.43–1.50 (m, 24H, CH2), 1.67 (m, 8H, CH2), 1.86 (m,
16H, CH2), 1.97 (m, 8H, CH2), 4.08 (t, JH,H =6.5 Hz, 16H, OCH2), 4.30
(t, JH,H =6.5 Hz, 8H, OCH2), 7.42 (s, 8H, ArH), 8.93 ppm (s, 8H, b-H);
13C NMR (125 MHz, CDCl3, 258C, TMS): d=14.0, 14.2, 22.6, 22.8, 26.1,
26.3, 29.2, 29.4, 29.5, 29.5, 29.7, 30.6, 31.8, 32.0, 69.4, 73.8, 114.3, 120.2,
137.1, 138.0, 151.2 ppm; HRMS (FD): m/z calcd for
C140H222N4O12:
2151.6884; found: 2151.6714, isotope profiles agree; elemental analysis
calcd (%) for C140H222N4O12: C 78.09, H 10.39, N 2.60; found: C 77.89,
H 10.47, N 2.60.
5,10,15,20-Tetrakis(3,4,5-trinonyloxyphenyl)porphyrin (4b). The reaction
mixture was passed through a short pad of alumina (alumina, CH2Cl2)
and all fractions containing porphyrin 4b were combined, evaporated to
dryness, and chromatographed (silica gel, hexanes/CH2Cl2 4:1 to 3:2) to
obtain porphyrin 4b contaminated with a blue-fluorescent compound.
Subsequent chromatography (DCVC, silica gel, hexanes/CH2Cl2 4:1 to
1:1) afforded pure porphyrin 4b as an amorphous dark violet solid
(138 mg, 37%). Rf =0.37 (silica gel, CH2Cl2/hexanes, 9:20); m.p.: 26.28C
(DSC, 18Cminꢀ1); UV/Vis (CH2Cl2): l (e)=425 (567000), 518 (25100),
555 (12000), 592 (6900), 649 nm (6900);1H NMR (500 MHz, CDCl3,
258C, TMS): d=ꢀ2.79 (brs, 2H, NH), 0.82–0.85 (m, 24H, CH3), 0.91–
0.94 (m, 12H, CH3), 1.23–1.41 (m, 112H, CH2), 1.45–1.52 (m, 24H, CH2),
3,4,5-Tridodecyloxybenzaldehyde (3e). To a solution of 3,4,5-trihydroxy-
benzaldehyde monohydrate (1; 4.49 g, 26.1 mmol) in DMF (160 mL), 1-
bromododecane (34.0 mL, 141.6 mmol) was added, followed by K2CO3
(9.71 g, 70.3 mmol) and KI (660 mg, 3.98 mmol). The reaction mixture
was stirred for 15 h at 1608C and further allowed to cool down to RT.
The product crystallized from the reaction mixture while cooling. The re-
sulting solid was washed with water, dissolved in EtOAc and dried
(Na2SO4). Then it was filtered and evaporated to dryness to give a brown
solid. Subsequently, the crude product was chromatographed (silica gel,
hexanes/CH2Cl2 4:1 to 3:7) to obtain pure aldehyde 3e (15.47 g, 90%)
which was recrystallized (EtOAc) to give colorless crystals. M.p.: 50.4–
51.38C (EtOAc) [lit. m.p.: 508C (propan-2-ol)];[14] 1H NMR (500 MHz,
CDCl3, 258C, TMS): d=0.88 (m, 9H, CH3), 1.26–1.36 (m, 48H, CH2),
1.45–1.51 (m, 6H, CH2), 1.72–1.78 (m, 2H, CH2), 1.80–1.85 (m, 4H,
CH2), 4.02–4.07 (m, 6H, OCH2), 7.08 (s, 2H, ArH), 9.83 ppm (s, 1H,
CHO). Other spectral and physical properties concur with published
data.[21]
1.66 (m, 8H, CH2), 1.86 (m, 16H, CH2), 1.97 (m, 8H, CH2), 4.08 (t, JH,H
=
6.5 Hz, 16H, OCH2), 4.29 (t, JH,H =6.5 Hz, 8H, OCH2), 7.41 (s, 8H,
ArH), 8.93 ppm (s, 8H, b-H); 13C NMR (125 MHz, CDCl3, 258C, TMS):
d=14.1, 14.2, 22.6, 22.8, 26.1, 26.3, 29.2, 29.4, 29.5, 29.5, 29.6, 29.8, 29.8,
30.6, 31.9, 32.0, 69.4, 73.8, 114.3, 120.2, 137.1, 138.0, 151.2 ppm; LRMS
(FD): m/z calcd for C152H246N4O12: 2319.9; found: 2319.8, isotope profiles
agree; elemental analysis calcd (%) for C152H246N4O12: C 78.64, H 10.68,
N 2.41; found: C 78.43, H 10.70, N 2.38.
5,10,15,20-Tetrakis(3,4,5-tridecyloxyphenyl)porphyrin (4c). The reaction
mixture was passed through a short pad of alumina (alumina, CH2Cl2)
and all fractions containing porphyrin 4c were combined, evaporated to
dryness, and chromatographed (silica gel, hexanes/CH2Cl2 9:1 to 3:2) to
obtain porphyrin 4c contaminated with a blue-fluorescent compound.
Subsequent chromatography (DCVC, silica gel, hexanes/CH2Cl2 3:1 to
3:2) afforded pure porphyrin 4c as a dark violet oil (156 mg, 39%). Rf =
0.41 (silica gel, CH2Cl2/hexanes, 9:20); m.p.: ꢀ54.68C (DSC, 108Cminꢀ1);
UV/Vis (CH2Cl2): l (e)=425 (523000), 518 (23200), 555 (11000), 593
(7000), 649 nm (5800);1H NMR (500 MHz, CDCl3, 258C, TMS): d=
ꢀ2.79 (brs, 2H, NH), 0.82–0.84 (m, 24H, CH3), 0.90–0.92 (m, 12H, CH3),
1.22–1.42 (m, 136H, CH2), 1.45–1.52 (m, 24H, CH2), 1.66 (m, 8H, CH2),
1.86 (m, 16H, CH2), 1.97 (m, 8H, CH2), 4.08 (t, JH,H =6.5 Hz, 16H,
OCH2), 4.29 (t, JH,H =6.5 Hz, 8H, OCH2), 7.41 (s, 8H, ArH), 8.93 ppm (s,
8H, b-H); 13C NMR (125 MHz, CDCl3, 258C, TMS): d=14.1, 14.1, 22.6,
22.7, 26.2, 26.3, 29.3, 29.4, 29.5, 29.5, 29.5, 29.6, 29.8, 29.8, 29.9, 30.6, 31.9,
32.0, 69.4, 73.8, 114.3, 120.2, 137.1, 138.0, 151.2 ppm; LRMS (FD): m/z
calcd for C164H270N4O12: 2488.1; found: 2488.2, isotope profiles agree; ele-
mental analysis calcd (%) for C164H270N4O12: C 79.11, H 10.93, N 2.25;
found: C 78.94, H 10.99, N 2.21.
3,4,5-Trioctadecyloxybenzaldehyde (3 f). To a solution of 3,4,5-trihydrox-
ybenzaldehyde monohydrate (1; 1.14 g, 6.6 mmol) in DMF (40 mL), 1-
bromooctadecane (8.72 g, 26.2 mmol) was added, followed by K2CO3
(2.42 g, 17,5 mmol) and KI (180 mg, 1.08 mmol). The reaction mixture
was stirred for 22 h at 1608C and further allowed to cool down to RT.
The product crystallized from the reaction mixture while cooling. The re-
sulting solid was washed with water, dissolved in CHCl3, and dried
(Na2SO4). Then it was filtered and evaporated to dryness to give a brown
solid. Subsequently, the crude product was chromatographed (silica gel,
hexanes/CHCl3 4:1 to 7:3) to obtain pure aldehyde 3d (5.86 g, 97%)
which was recrystallized (hexanes/EtOAc) to give colorless crystals. M.p.:
73.3–758C (hexanes/EtOAc) (lit. m.p.: 75–768C);[15] 1H NMR (500 MHz,
CDCl3, 258C, TMS): d=0.88 (m, 9H, CH3), 1.26–1.36 (m, 84H, CH2),
1.45–1.59 (m, 6H, CH2), 1.72–1.78 (m, 2H, CH2), 1.80–1.85 (m, 4H,
CH2), 4.02–4.07 (m, 6H, OCH2), 7.08 (s, 2H, ArH), 9.83 ppm (s, 1H,
CHO). Other spectral and physical properties concur with published
data.[22]
General procedure for porphyrins synthesis: Samples of an aldehyde
(0.64 mmol) and pyrrole (56 mL, 0.81 mmol) were dissolved in CH2Cl2
(64 mL) at room temperature (in the case of some solid aldehydes, gentle
heating to 408C was necessary). Then TFA (78 mL) and BF3·Et2O
(2.4 mL) were added while stirring. After 2.5 h, a solution of DDQ
(110 mg, 0.49 mmol) in THF (6.0 mL) was added, and the reaction mix-
ture was stirred at RT for an additional 1 h. The purification details are
described for each case as follows.
5,10,15,20-Tetrakis(3,4,5-triundecyloxyphenyl)porphyrin (4d). The reac-
tion mixture was passed through a short pad of alumina (alumina,
CH2Cl2) and all fractions containing porphyrin 4d were combined, evapo-
rated to dryness, and chromatographed (silica gel, hexanes/CH2Cl2 9:1 to
3:2) to obtain porphyrin 4d contaminated with a blue-fluorescent com-
pound. Subsequent chromatography (DCVC, silica gel, hexanes/CH2Cl2
4:1 to 13:7) afforded pure porphyrin 4d as a violet oil (227 mg, 53%).
Rf =0.48 (silica gel, CH2Cl2/hexanes, 9:20); m.p.: ꢀ23.88C (DSC,
58Cminꢀ1); UV/Vis (CH2Cl2): l (e)=425 (412000), 518 (18300), 555
(8400), 591 (5500), 649 nm (4400);1H NMR (500 MHz, CDCl3, 258C,
TMS): d=ꢀ2.79 (brs, 2H, NH), 0.82–0.85 (m, 24H, CH3), 0.88–0.92 (m,
12H, CH3), 1.22–1.34 (m, 160H, CH2), 1.46–1.52 (m, 24H, CH2), 1.64–
1.70 (m, 8H, CH2), 1.86 (m, 16H, CH2), 1.94–2.00 (m, 8H, CH2), 4.08 (t,
5,10,15,20-Tetrakis(3,4,5-trioctyloxyphenyl)porphyrin (4a). The reaction
mixture was passed through a short pad of alumina (alumina, CH2Cl2)
and all fractions containing porphyrin 4a were combined, evaporated to
dryness, and chromatographed (silica gel, hexanes/CH2Cl2 3:1 to 1:1) to
obtain porphyrin 4a contaminated with a blue-fluorescent compound.
Subsequent chromatography (DCVC, silica gel, hexanes/CH2Cl2 4:1 to
1:1) afforded pure porphyrin 4a as a violet solid (124 mg, 36%). Rf =0.31
(silica gel, CH2Cl2/hexanes, 9:20); m.p.: 55.18C (DSC, 58Cminꢀ1); UV/
Vis (CH2Cl2): l (e)=425 (548000), 518 (24100), 555 (11500), 592 (7200),
J
H,H =6.5 Hz, 16H, OCH2), 4.29 (t, JH,H =6.5 Hz, 8H, OCH2), 7.42 (s, 8H,
ArH), 8.93 ppm (s, 8H, b-H); 13C NMR (125 MHz, CDCl3, 258C, TMS):
d=14.0, 14.1, 22.6, 22.7, 26.2, 26.3, 29.3, 29.5, 29.6, 29.6, 29.6, 29.8, 29.8,
29.8, 29.9, 30.6, 31.9, 32.0, 69.4, 73.8, 114.4, 120.2, 137.1, 138.1, 151.2 ppm;
Chem. Asian J. 2010, 5, 904 – 909
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
907

D. T. Gryko et al.
FULL PAPERS
LRMS (FD): m/z calcd for C176H294N4O12:2656.2; found: 2656.2, isotope
profiles agree; elemental analysis calcd (%) for C176H294N4O12: C 79.52,
H 11.15, N 2.11; found: C 79.26, H 11.21, N 2.06.
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5,10,15,20-Tetrakis(3,4,5-tridodecyloxyphenyl)porphyrin (4e). The reac-
tion mixture was passed through a short pad of alumina (alumina,
CH2Cl2) and all fractions containing porphyrin 4e were combined and
evaporated to dryness. Two repetitive column chromatography (silica gel,
hexanes/CH2Cl2 2:3 to 1:1) afforded pure porphyrin 4e as a violet solid
(209 mg, 46%). Rf =0.52 (silica gel, CH2Cl2/hexanes, 9:20); m.p.: 36.48C
(DSC, 18Cminꢀ1); UV/Vis (CH2Cl2): l (e)=425 (437000), 518 (21300),
554 (9900), 592 (6500), 649 nm (5600);1H NMR (500 MHz, CDCl3, 258C,
TMS): d=ꢀ2.79 (brs, 2H, NH), 0.83–0.85 (m, 24H, CH3), 0.88–0.91 (m,
12H, CH3), 1.22–1.34 (m, 184H, CH2), 1.46–1.52 (m, 24H, CH2), 1.67 (m,
8H, CH2), 1.86 (m, 16H, CH2), 1.97 (m, 8H, CH2), 4.08 (t, JH,H =6.4 Hz,
16H, OCH2), 4.30 (t, JH,H =6.5 Hz, 8H, OCH2), 7.42 (s, 8H, ArH),
8.94 ppm (s, 8H, b-H); 13C NMR (125 MHz, CDCl3, 258C, TMS): d=
14.1, 22.6, 26.2, 29.3, 29.4, 29.5, 29.6, 29.6, 29.6, 29.6, 29.7, 29.8, 29.8, 29.8,
31.9, 32.0, 69.4, 73.8, 114.4, 120.2, 137.1, 138.1, 151.2 ppm; LRMS (FD):
m/z calcd for C188H318N4O12:2824.4; found: 2824.3, isotope profiles agree;
elemental analysis calcd (%) for C188H318N4O12: C 79.89, H 11.34, N 1.98;
found: C 79.82, H 11.22, N 1.87.
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Rf =0.67 (silica gel, CH2Cl2/hexanes, 9:20); m.p.: 44.08C (DSC,
18Cminꢀ1); UV/Vis (CH2Cl2): l (e)=425 (450000), 518 (19400), 555
(8800), 592 (5700), 649 nm (4600);1H NMR (500 MHz, CDCl3, 258C,
TMS): d=ꢀ2.79 (brs, 2H, NH), 0.85–0.89 (m, 36H, CH3), 1.21–1.34 (m,
328H, CH2), 1.46–1.52 (m, 24H, CH2), 1.67 (m, 8H, CH2), 1.86 (m, 16H,
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J
H,H =6.5 Hz, 8H, OCH2), 7.41 (s, 8H, ArH), 8.93 ppm (s, 8H, b-H);
13C NMR (125 MHz, CDCl3, 258C, TMS): d=14.1, 14.1, 22.7, 22.7, 26.2,
29.3, 29.4, 29.5, 29.6, 29.6, 29.7, 29.7, 29.8, 29.8, 29.8, 29.8, 29.9, 31.9, 31.9,
69.4, 73.8, 114.4, 120.2, 137.1, 138.1, 151.3 ppm; LRMS (FD): m/z calcd
for C260H462N4O12: 3833.6; found: 3833.4, isotope profiles agree; elemen-
tal analysis calcd (%) for C260H462N4O12: C 81.40, H 12.14, N 1.46; found:
C 81.17, H 12.16, N 1.45.
Acknowledgements
We thank US Air Force (Contract: FA8655-07-1-3020) and The Founda-
tion for Polish Science (A.N.K. Ventures Program), Dr Beata Mossety-
Leszczak and MSc Piotr Murias for measurements as well as Prof. Ewa
Gꢁrecka and Dr Damian Pociecha for helpful discussions, and Dr David
Will for amending the manuscript.
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Received: December 3, 2009
Published online: March 16, 2010
[18] When this manuscript was under preparation, Japanese chemists pa-
tented porphyrins of the same general structure: S. Maruyama, W.
Saito, WO/2009/113511.
Chem. Asian J. 2010, 5, 904 – 909
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
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